System Reset (with built-in watchdog timer) MM1095 MITSUMI System Reset (with built-in watchdog timer) Monolithic IC MM1095 Outline This IC functions in a variety of CPU systems and other logic systems to generate a reset signal and reset the system accurately during momentary interruption or lowering of power supply voltage. It also has a built-in watchdog timer for operation diagnosis. This prevents the system from running wild by generating an intermittent reset pulse during system mis-operation. Features 1. 2. 3. 4. 5. Built-in watchdog timer Low minimum operating voltage Low operating limit voltage Watchdog stop function (RCT pin) Few external parts 100µA typ. Vcc=0.8V Package DIP-8B (MM1095AD, MM1095BD) SOP-8C (MM1095AF, MM1095BF) SIP-8A (MM1095AS, MM1095BS) Applications 1. Reset circuits in microcomputers, CPUs and MPUs 2. Logic circuit reset circuits 3. Microcomputer system monitoring, etc. Pin Assignment 8 1 7 2 6 3 5 4 1 TC 1 TC 2 NC 2 NC 3 CK 3 CK 4 GND 4 GND 5 VCC 5 VCC 6 RCT 6 RCT 7 VS 1 2 3 4 5 6 7 8 SIP-8A 7 ------------------------------------------ SOP-8C/DIP-8B 8 RESET VS ------------------------------------------ 8 RESET System Reset (with built-in watchdog timer) MM1095 MITSUMI Pin Description Pin No. Name Function TWD, TWR, TPR variable pins 1 . (TWD, TWR and TPR times are determined TC by the external capacitor.) 2 N.C 3 CK 4 GND 5 VCC Voltage detection 6 RCT Watchdog timer stop pin 7 TPR (mS)=5000 CT (µF) TWD (mS)=500 CT (µF) TWR (mS)=100 CT (µF) Clock input pin, inputs clock from logic system GND pin VS MM1095A 3.2V, MM1095B 4.2V Operation modes : Operation OPEN, Stop connect to GND Detection voltage variable pin ------------------------------------------------------------------------------------ 8 RESET Reset output pin (low output) Absolute Maximum Ratings Item Symbol Rating Units Power supply voltage VCC max. -0.3~+10 V CK pin input voltage VCK -0.3~VCC+0.3 ( <= +10) V VS pin input voltage VVS -0.3~VCC+0.3 ( <= +10) V Voltage applied to RCT pin VRCT -0.3~VCC+0.3 ( <= +10) V Voltage applied to RESET pin VOH -0.3~VCC+0.3 ( <= +10) V Allowable loss Pd 400 mW Storage temperature TSTG -40~+125 °C -------------------------------------------- Recommended Operating Conditions Item Symbol Rating Units Power supply voltage VCC +2.2~+7.0 V RESET sync current IOL 0~1.0 mA Clock monitoring time setting TWD 0.1~1000 mS Clock rise and fall times tFC, tRC <100 µS TC pin capacitance CT 0.0002~2 µF Operating temperature TOP -25~+75 °C ------------------------------------------- System Reset (with built-in watchdog timer) MM1095 MITSUMI Electrical Characteristics (DC) Item Consumption MM1095A current MM1095B MM1095A Detection MM1095B voltage MM1095A MM1095B Detection voltage temperature coefficient Hysteresis voltage MM1095A MM1095B CK input threshold CK input current Output voltage MM1095A (High) MM1095B Output voltage (Low) R output sync current CT charge current Minimum operating power -------------------------------------------------------------------------- supply voltage to ensure RESET (Except where noted otherwise, MM1095A : Vcc=3.6V, Ta = 25°C, MM1095B: Vcc=5.0V) Symbol Measurement conditions ICC During watchdog timer operation VSL VSH VS=OPEN, VCC VS=OPEN, VCC Min. Typ. Max. 100 150 130 195 3.10 3.20 3.30 4.05 4.20 4.35 3.15 3.25 3.35 4.15 4.30 4.45 VS/ T VHYS 25 50 100 50 100 150 0.8 1.2 2 0 1 -12 -6 -2 I RESET =-1µA ------------------------------------------ 3.0 3.4 VS=OPEN 4.0 4.5 VTH IIH A : VCK=3.6V, B : VCK=5.0V IIL VCK=0V VOH VOL1 V mV V µA V ------------------------------------------ 0.2 0.4 ------------------------------------------ 0.3 0.5 I RESET =0.5mA, VS=0V µA %/°C ±0.01 VSH-VSL, VCC Units V VOL2 I RESET =1.0mA, VS=0V IOL V RESET =1.0V, VS=0V 1 2 ICT1 VTC=1.0V during watchdog timer operation -1.60 -2.40 -4.80 µA ICT2 VTC=1.0V during power ON reset operation -0.16 -0.24 -0.48 µA 0.8 1.0 V ------------------------------------------ mA ------------------------------------------ VCCL V RESET =0.4V ------------------------------------------ I RESET =0.1mA System Reset (with built-in watchdog timer) MM1095 MITSUMI Electrical Characteristics (DC) Item VCC input pulse width Symbol MM1095A Measurement conditions VCC TPI MM1095B VCC CK input pulse width TCKW CK input cycle TCK Watchdog timer monitoring time 1 (Except where noted otherwise, MM1095A : VCC=3.6V, Ta=25°C, MM1095B : VCC=5.0V) 3.6V Min. Typ. Max. Units 8 2.8V µS 5.0V 8 4.0V CK or 3 µS 20 µS TWD CT=0.02µF 5 10 15 mS TWR CT=0.02µF 1 2 3 mS 50 100 150 mS 2 10 µS 2.0 4.0 µS 0.2 1.0 µS * Reset time for watchdog timer 2 * Reset hold time for power supply rise 3 TPR * Output delay time from VCC 4 * Output rise time 5 * Output fall time 5 * TPD tR CT=0.02µF, VCC VCC ------------------------------------------------------------------------------- RESET pin, RL=10kΩ, CL=20pF ------------------------------------------------------------------------------- RESET pin, RL=10kΩ, CL=20pF ------------------------------------------------------------------------------- tF RESET pin, RL=10kΩ, CL=20pF Notes: 1 Monitoring time is the time from the last pulse (negative edge) of the timer clear clock pulse until reset pulse output. In other words, reset output is output if a clock pulse is not input during this time. 2 Reset time means reset pulse width. However, this does not apply to power ON reset. 3 Reset hold time is the time from when VCC exceeds detection voltage (VSH) during power ON reset until reset release (RESET output high). 4 Output delay time is the time from when power supply voltage drops below detection voltage (VSL) until reset (RESEToutput low). 5 Voltage range when measuring output rise and fall is 10~90%. 6 Watchdog timer monitoring time (TWD), watchdog timer reset time (TWR) and reset hold time (TPR) during power supply rise can be changed by varying CT capacitance. The times are expressed by the following formulae. * * * ------------------------------------------------------------------------------- * * * . TPR (mS) =. 5000 CT (µF) TWD (mS) .=. 500 CT (µF) TWR (mS) .=. 100 CT (µF) Example: When CT=0.02µF TPR .=. 100mS TWD .=. 10mS TWR .=. 2mS System Reset (with built-in watchdog timer) MM1095 MITSUMI Measuring Circuits Measuring Circuit 1(DC) Measuring Circuit 1 Item Measuring Circuit 2 (AC) SW & Power Supply Table Symbol SW1 SW2 SW3 SW4 SW5 SW6 SW7 Consumption current Detection voltage CK input threshold CK input current Output voltage (High) ICC OFF OFF OFF ON ON ON A ------------------------------------------------------- VCC VCK VCT I RESET VM, IM 3.6V 3.6V 0V - ICC VSL OFF OFF ON ON ON ON A 3.6V 3V 0V 2V - VO1, CRT1 VSH OFF OFF ON ON ON ON A 3V 3.6V 0V 2V - VO1, CRT1 VTH OFF OFF OFF ON ON ON A 3.6V 0V 3V 1V - ICK, VCK IIH OFF OFF OFF ON ON ON A 3.6V 3.6V 0V - ICK IIL OFF OFF OFF ON ON ON A 3.6V 0V 0V - ICK VOH ON OFF ON ON ON ON A 3.6V 3.6V 2V -1µA VO1 VOL1 ON ON ON ON ON ON A 3.6V 3.6V 2V 0.5mA VO1 VOL2 ON ON ON ON ON ON A 3.6V 3.6V 2V 1.0mA VO1 Output sink current IOL1 OFF ON ON ON ON ON B 3.6V 3.6V 2V - I O1 CT charge current 1 ITC1 OFF OFF OFF ON ON OFF A 3.6V - 1V - ITC CT charge current 2 ITC2 OFF OFF OFF ON ON OFF A 3.6V - 1V - ITC VCCL ON OFF ON ON ON ON A 0V 2V 0V 0V - VO1, VCC VCK CRT Output voltage (Low) Minimum operating power -------------------------------------------------- supply voltage to ensure RESET Measuring Circuit 2 Item Symbol SW1 SW2 VCCA 3.6V T1 VCC T2 1.4V T3 CK input pulse width TCKW A B - 3.6V TCK A B - 3.6V TWD A A - 3.6V - 3.6V TWR A A - 3.6V - 3.6V TPR B A A - 3.6V - 3.6V - - 0V CRT1 Watchdog timer monitoring time Reset time for watchdog timer Reset hold time for power supply rise Output delay time 3.6V 0V 1.4V - CRT1 B 2.5V - VCKA C CK input cycle T2 or 0V T2 1.4V 0V T2 T3 - CRT2 CRT1 CRT2 CRT1 CRT2 CRT1 CRT2 CRT1 CRT2 CRT1 CRT2 TPD C A Output rise time TR A A - 3.6V - 3.6V CRT1 Output fall time TF A A - 3.6V - 3.6V CRT1 from VCC VO=1V SW & Power Supply Table TP1 VCC input pulse width Notes 0V Notes T1=8µS T2=3µS T3=20µS System Reset (with built-in watchdog timer) MM1095 MITSUMI Block Diagram MM1095A MM1095B RA RB ~ - 305k ~ - 350k ~ - 195k ~ - 150k Note 1 : CP=0.1µF approx. Note 2 : C=1000pF Note 3 : The watchdog timer can be stopped by connecting the RCT pin to GND. (Then it functions as a voltage detection circuit.) Timing Chart VCC VSH VSL CK CT TCK TPR RESET 1 2 TWD 3 4 5 5 TPR TWR 6 7 8 9 10 11 12 System Reset (with built-in watchdog timer) MM1095 MITSUMI Description of Operation ------------------------------------------------- 1. RESET goes low when VCC rises to approximately 0.8V. 2. Capacitor CT charging starts when VCC rises to VSH (MM1095A .=. 3.25V, MM1095B .=. 4.3V). Output is in reset state at this time. 3. Output reset is released (RESET goes high) after a certain time (TPR), from when CT starts charging until discharge (the time from when CT voltage reaches a certain threshold value 1 (.=. 1.4V) until CT voltage drops to a certain threshold value 2 (.=. 0.2V). Approximately 1µA (VCC=0.8V) of pull up current is output from RESET. Reset hold time : TPR is as follows. TPR (mS) .=. 5000 CT (µF) CT charging starts again after reset release, and watchdog timer operation begins. 4. If a clock is input (negative edge trigger) to the CK pin during CT charging, charging switches to discharge. 5. Discharge switches to charging when CT voltage drops to a certain threshold value (.=. 0.2V). Steps 4 and 5 are repeated while a normal clock is input from the logic system. 6. Output goes to reset state (RESET goes low) when the clock ceases and CT voltage reaches reset ON threshold value (.=. 1.4V). The formula for CT charging time (TWD: watchdog timer monitoring time) until reset is output is as follows. TWD (mS) .=. 500 CT (µF) 7. Watchdog timer reset time TWR is the discharge time until CT voltage drops to reset OFF threshold value . ( =. 0.2V). The formula is as follows. TWR (mS) .=. 100 CT (µF) After reset OFF threshold value is reached, output reset is released and CT starts charging. Thereafter, steps 4 and 5 are repeated if a normal clock is input, and when the clock ceases, 6 and 7 are repeated. 8. Reset is output when VCC drops to VSL (MM1095A .=. 3.2V, MM1095B .=. 4.2V). CT is charged simultaneously. 9. CT charging starts when VCC rises to VSH. When Vcc drops momentarily, CT charging begins after the charge is first discharged, if the time from VCC dropping below VSL until it rises to VSH is longer than the VCC input pulse width standard value TPI. 10.Output reset is released after VCC goes above VSH and after TPR, and the watchdog timer starts. Thereafter, 8~10 are repeated when VCC goes below VSL. 11.When power is OFF, reset is output if VCC goes below VSL. 12.When VCC drops to 0V, reset output is held until VCC reaches 0.8V. --------------------------------------------- ---------------------------------------------